A typical oil pan is placed beneath a cylinder block and crank shaft of an internal combustion engine. The oil pan is configured to receive oil that drains or is otherwise exhausted from the cylinder block and the crank shaft and/or main bearings that support the crank shaft. The oil collects in a sump of the oil pan and is then pumped from a sump pick-up location into a lubrication system associated with the engine. The oil pan is subject to loud noise and vibrations emanating from the engine.
Traditional means for reducing radiated sound from engine components include damping of structural resonance, acoustic absorption of sound through acoustic absorption covers, and isolation of the engine component from the source of vibration input energy at the site of attachment.
The proper selection of the most effective solution is known after it is determined whether the radiated noise is the result of a resonant response or forced response. Resonant response refers to the tendency of a system to amplify more oscillatory energy directed at it at the frequencies that match the system's natural frequency of vibration than at other frequencies i.e the system radiates more noise at the resonant frequencies of the system. Forced response refers to a system that radiates noise in a broad frequency range. Unlike resonant response, there is no dominant specific radiation frequency in forced response.
Acoustic absorption covers cannot be implemented on oil pans in production as the materials used for acoustic absorption covers deteriorate under exposure to the under-vehicle environment of salt, water, stones, road debris, and the close proximity to high temperature exhaust system components within the package space available. The method of attachment isolation of the engine component cannot be used in cast aluminum engine oil pans because they are structural components that must react to powertrain-bending forces.